• 경영과학
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• 제24권2호
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• pp.81-93
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• 2007

Achieving a target operational availability is more economical and efficient than having many quantities of the weapon system, since the cost of weapon system becomes expensive. The intent of this study is twofold; first, we develop the simulation model to determine the optimal inventory level of the maintenance float while achieving a target operational availability of the Korean-made helicopter. The quantity decision model considers following factors such as a reliability. a turn around time(TAT). a protection level for inventory, and so on. Second, we analyze whether the existence of a lateral transshipment among bases and the reduction of TAT relate to an inventory level and the operational availability. The research result shows that both TAT and lateral transshipment have an effect on reducing the inventory level of the maintenance float and improving an operational availability.

• 한국대기환경학회지
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• 제34권2호
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• pp.342-355
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• 2018

Emission inventory (EI) is often recognized as a foundational pillar for air quality planning. In this manuscript, we reviewed national emission inventory (NEI) development processes in United States(US) and made recommendations for South Korean emission inventory development for the future. First, we examined history of emission inventory development in US while focusing on what has been success and failure. We noticed that, in general, emission reductions led to air pollution abatement although efficacy of same degree of reduction may not result in similar air quality improvement. Second, we described conventional approaches of developing NEI and differences between NEI and EI for State Implementation Plan which is required for air quality management in US. Last, we analyzed how US Environmental Protection Agency and counterpart agencies in states came up with a new plan for the next major regulatory modeling project. Based on our analysis, we conclude that early and steady participation of local governments will lead to effective and efficient emission inventory development and, in turn, will result in successful air quality planning that is necessary for actual air quality improvement.

• 디지털융복합연구
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• 제11권12호
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• pp.265-274
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• 2013

글로벌 경제 침체와 국내 경기변동은 기업의 자금 조달에 어려움을 초래하고 기업 운영을 악화시킨다. 특히 불황기에 직면한 기업이 많은 재고를 보유하고 있다면 운영관리 뿐만 아니라 심각한 자금 조달 문제가 발생할 수 있다. 그것은 경쟁적 우위 차원에서 경영 전략을 수립하여야 되는 기업의 사기를 좌절시킬 수 있다. 이렇게 운전자금 부족이나 운전자금 문제를 겪는 기업은 우선 재고투자 감축을 고려하게 되지만 재고투자 감축 정책은 재고 운영비용을 증가시킬 수 있다. 만일 비용 증가 폭이 크다면 재고감축 정책의 타당성이 성립되지 않는다. 본 연구는 재고투자 감축 크기에 비교해서 총비용의 변화가 크지 않음을 제시하고 민감도 분석을 통해 나타내고 있다. 이 결과는 재고 운영 정책에 따라서는 운전자금 부족 문제가 발생하였을 때 재고투자 감축의 정당성을 제안하고 있다. 여기서 전개한 재고모형은 최대한 현실성을 고려하여 개발하였다.

• 경영과학
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• 제11권1호
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• pp.73-90
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• 1994

Recently the recongnition of Logistics becomes important to enterpries as a means for improving their competition, but the Korea enterpries falls for far behind in management techniques for analyzing realities and problems in the Logistics compare to the advanced countries. Especially the function of inventory control which is most undeveloped in them should be improved in Korea. Inventory is very important in Logistics, but there exists trade-off between inventory level and customer in the service level. It is difficult to coordinate both the reduction in the inventory level and the enhancement in the service level. Its effective technique is a DRP system. In general, it deals with arborescent distribution network in which a given channel member has a single source of supply. This article aims to present a DRP system, and more a DRP system which is flexible and responsive in the multisourcing, multi-echelon distribution network. Related research issues are discussed. Finally, using a DRP system on logistics and the management performance. So we can help the physical distribution improvement of the Korean enterprises.

• 산업경영시스템학회지
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• 제42권4호
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• pp.61-68
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• 2019

Currently many companies are interested in reduction of the carbon emissions associated with their supply chain activities such as transportation and operations. Operational decisions, such as modifications in order quantities could an effective way in reducing carbon emissions in the supply chain. Cap-and-trade regulation, sometimes called emissions trading, is a market-based tool to limit greenhouse gas emissions. Under cap-and-trade regulation, emission credits are allocated to the firms and the firms trades emissions under cap-and-trade schemes. In this paper, we propose a single-manufacturer single-buyer two-echelon supply chain problem under the cap-and-trade mechanism incorporating the carbon emissions caused by transportation and warehousing activities where a single manufacturer produces a family of items in order to deliver a family of items to a single buyer at a fixed interval of time for effective implementation of Just-In-Time (JIT) Purchasing. An integrated multi-product lot-splitting model of facilitating multiple shipments in small lots between buyer and manufacturer is developed in a JIT Purchasing environment. Also, an iterative heuristic algorithm is developed to derive the common order interval, the number of intervals for each product and the number of shipments between the buyer and the manufacturer during the common interval. A numerical example is given to illustrate the savings in reduction of total cost and carbon emissions by the inventory model incorporating cap-and-trade mechanism compared to the classical inventory model. The proposed inventory model could be useful for the practical solution of two-echelon supply chain inventory problem under cap-and-trade mechanism.

• 한국항해항만학회지
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• 제34권2호
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• pp.131-136
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• 2010

The aim of the paper is to solve the problem of customer reduction due to the difficulty of parts sourcing which impacts production delay and delivery delay in SC networks. Furthermore, this paper is to suggest the new inventory policy of MTS in order to solve the problem of current inventory policy. In order to compare two policies, a LCD maker is selected as a case study and the real data for 2007 years is used for simulation input. The maker uses MTO policy for parts sourcing which has the problem of lead time even if it has some advantage of inventory cost. Based on current process. The simulation program of AS-IS model and TO-BE model using ARENA 10 version is developed for evaluation. In a result, the order number of two policies shows that MTO is 52 and MTS is 53. However the quantity of order shows big difference such that MTO is 168,460 and MTS is 225,106. Particularly, the lead time of new inventory policy shows much shorter that that of MTO such that MTO 100 is days and MTS is 16 days. In spite of short lead time by MTS policy, new policy has to take burden of inventory cost per year. Total inventory cost per year by MTS policy is US$ 11,254 and each part inventory cost is that POL is US$ 1,807, LDI is US$ 2,166 and Panel is US$ 7,281. The implication of the research is that the company has to consider the cost and the service simultaneously in deciding the inventory policy. In the paper, even if the optimal point of deciding is put into tactical area, the ground of decision is suggested in order to improve the problem in SC networks.

• 한국대기환경학회지
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• 제33권2호
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• pp.139-158
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• 2017

CMAQ (Community Multiscale Air Quality Model) simulations were carried out to estimate the potential range of contributions on surface $PM_{2.5}$ concentrations over the Seoul Metropolitan Area (SMA) with the gaseous precursors and Primary Particulate Matters(PPM) available from a recent national emissions inventory. In detail, on top of a base simulation utilizing the 2013 Clean Air Policy Supporting System (CAPSS) emission inventory, a set of Brute Force Method (BFM) simulations after reducing anthropogenic $NO_x$, $SO_2$, $NH_3$, VOCs, and PPM emissions released from area, mobile, and point sources in SMA by 50% were performed in turn. Modeling results show that zero-out contributions(ZOC) of $NH_3$ and PPM emissions from SMA are as high as $4{\sim}5{\mu}g/m^3$ over the region during the modeling period. On the contrary, ZOC of local $NO_x$ and $SO_2$ emissions to SMA $PM_{2.5}$ are less than $1{\mu}g/m^3$. Moreover, model analyses indicate that a wintertime $NO_x$ reduction at least up to 50% increases SMA $PM_{2.5}$ concentrations, probably due to increased HNO3 formation and conversion to aerosols under more abundant ozone and radical conditions after the $NO_x$ reduction. However, a nation-wide $NO_x$ reduction decreased SMA $PM_{2.5}$ concentrations even during winter, which implies that nation-wide reductions would be more effective to curtail SMA $PM_{2.5}$ concentrations than localized efforts.

• 한국건설관리학회:학술대회논문집
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• 한국건설관리학회 2006년도 정기학술발표대회 논문집
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• pp.702-707
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• 2006

건설자재의 경우 물량 확보 차원과 소량 반입의 어려움, 공정 지연 등의 이유로 인하여 현장에 상당량의 재고를 보유하여 왔다. 특히 철근의 경우 변동요인이 많아 일반적으로 1개월 이상의 여유 재고를 보유하여 왔다. 하지만 이렇게 재고의 규모가 필요이상으로 과도할 경우 재고유지비용이 증가하게 되고 자재적치에 많은 공간이 소요되어 현장 내 이동에 불편을 겪을 수도 있으며 생산성이 저하 되어 낭비요인으로 작용하게 된다. 반면에 재고량이 부족할 경우에는 예상치 못했던 수요가 발생하거나 자재수급에 어려움이 생기는 경우 대응하기가 어려우며 자재부족에 따라 작업수행에 지연을 가져오게 되어 추가비용을 발생시킨다. 본 연구는 건설현장의 여러 가지 자재 중에서 구성 비율이 가장 높고 지속적인 수요에 의해 작업이 이루어지는 철근자재를 대상으로 재고관리 현황을 살펴보고 적정 재고관리 방안을 제시하였다. 먼저 일반적인 재고의 개념 및 재고관리 시스템에 대하여 살펴보고 철근 가공 ${\cdot}$ 조립과정의 적용성 여부를 판단하였다. 이후 자재의 리드타임 변이와 리드타임 동안의 자재의 수요율 변이를 고려하여 자재의 재주문 시점을 언제로 할 것인지를 결정하고 주문비용 및 재고유지비용, 자재 수요량을 고려하여 주문량을 얼마로 할 것인지를 결정하는 방법을 제시하였다.

• 산업경영시스템학회지
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• 제18권35호
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• pp.131-138
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• 1995

For the purpose of the reduction of tile cost, a production/inventory model including the interference phenomenon was developed. By investigating the cause and the characteristics of the direct/indirect cost due to the interference phenomenon, a strategy for suitable production was developed. The developed model was quantitatively validated using an existing-EPQ model and the SIMAN package was used to simulate and animate the model. Consequently, it was presented that the total operating cost of the system could be decreased with tile proposed model.

• 산업경영시스템학회지
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• 제42권1호
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• pp.158-166
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• 2019

In pursuing carbon emission reduction efforts, companies have focused for the most part on reducing emissions due to the more efficient equipment and facilities. However they overlook a significant source of carbon emissions, one that is driven by operational policies. Currently companies are looking for solutions to reduce carbon emissions associated with their operations. Operational adjustments, such as modifications in order quantities could an effective way in reducing carbon emissions in the supply chain. Also, Cap-and-Trade mechanism is generally accepted as on of the most effective market-based mechanism to reduce carbon emissions. In this paper, we investigate a supply chain with single manufacturer and multiple retailers multi-product inventory model under the cap-and-trade system incorporating the carbon emissions caused by transportation and warehousing activities. Also, we provide an iterative solution algorithm and derive the common order interval and the number of intervals for each product. We show by numerical example that the inventory model incorporating cap & trade mechanism can reduce total cost and carbon emissions compared to the classical inventory model. Using the numerical examples, we also investigates different carbon price on the performance of the inventory model.